A conventional fuel cell stack having a laminate or stack of unit cells is described in Japanese Laid-Open Patent Application Publication No. 2003-203670, for example. The fuel cell stack described in Japanese Laid-Open Patent Application Publication No. 2003-203670 has a laminate sandwiched with end plates, and both end plates are connected by a tension plate to maintain a pressurized state of the laminate. Further, the fuel stack has a first layer of low friction characteristics and insulating property and a second layer of buffer characteristics interposed between the laminate and the tension plate to absorb vibration and shock from the outside.
According to the fuel cell stack of the prior art described above, since the buffer material (second layer) is a spring element, increasing in resonant frequency (natural frequency) of the laminate leads to improved performance of vibration resistance. However, in a structure in which a cushioning material and the like are interposed between the tension plate and the laminate, there is a problem of increase in the number of components or parts count. Thus, it has been an issue or challenge to solve such a problem.